Many roller conveyors that use motor-incorporating rollers are used in factories and distribution warehouses. The motor-incorporating roller includes a roller body, a motor, and a reduction gear, the motor and the reduction gear being incorporated in the roller body. The roller body is rotated by driving the motor. There is a motor-incorporating roller provided with no reduction gear.
In a typical roller conveyor that uses a motor-incorporating roller, the motor-incorporating roller and an idling roller are attached to a frame which is provided with members arranged in parallel to each other, and, for example, a belt is wound around the motor-incorporating roller and the idling roller.
In the above roller conveyor, power supply to the motor-incorporating in the motor-incorporating roller causes rotation of the roller body of the motor-incorporating roller. The rotation is transmitted to the idling roller by the belt to rotate all the rollers attached to the frame to thereby convey a conveyance object.
In recent years, there has been used a roller conveyor in which a conveyance line is divided into a plurality of control zones. A control system when a roller conveyor is divided into a plurality of zones is referred to as decentralized control.
A roller conveyor that employs decentralized control does not allow the entire roller conveyor to integrally operate, but allows a motor-incorporating roller to rotate in each control zone to convey a conveyance object. Thus, the roller conveyor that employs decentralized control has less wasteful rotation of the motor-incorporating roller and thus has cost effectiveness. Further, dividing a range for control into small ranges eliminates the necessity of a complicated control system.
On the other hand, however, in the roller conveyor that has a plurality of control zones, the frequency of starting and stopping the motor-incorporating rollers is high. Thus, a gear, a belt, and a metal fitting which fixes the motor-incorporating roller to the frame are likely to be worn.
In particular, when the metal fitting which fixes the motor-incorporating roller to the frame is worn and a fixed shaft of the motor-incorporating roller rotates relative to the frame, for example, an electric supply line which allows the inside and the outside of the motor-incorporating roller to connect with each other is twisted off, which causes an unusable state of the motor-incorporating roller. Thus, when the fixed shaft of the motor-incorporating roller rotates relative to the frame, the conveyor is forced to stop for a long time.
Thus, maintenance of the roller conveyor is important. However, determination of the degree of wear of each consumable article largely depends on determination by human such as rule of thumb, calculation from an introduction time, determination by touching with hand, and determination based on sound or smell, and is thus not easy.
Patent Document 1 discloses an equipment diagnosis method capable of easily determining replacement time of a consumable member in a device such as a motor (electric motor). In the equipment diagnosis method disclosed in Patent Document 1, a current value of the motor in no-load running when the device is in a sound state is compared with a current value of the motor in a no-load running during operation, and the replacement time is determined based on a difference between the current values.
Patent Document 2 discloses a method for performing failure diagnosis by previously storing a profile of the relationship between current and time when a conveyor normally functions as reference information and comparing a current profile with the stored profile.